1. Technical Field
Example embodiments of the present invention relate to device-to-device communication, and more specifically, to a method of operating a network that performs switching between cellular communication and device-to-device communication in order to provide service continuity between the cellular communication and the device-to-device communication.
2. Related Art
Recently, in a cellular mobile communication system, a scheme for direct communication between a device and a device has been discussed. This is because there is a need for a network capacity, a data transfer rate, good service quality and the like for providing service to many users with rapid increase in data traffics due to the spread of various communication terminals.
Direct communication between mobile communication devices, namely, device-to-device communication (D2D) is considered as a scheme for meeting users' requirements by improving performance of an existing mobile communication system at low cost.
A device is a term indicating a communication terminal included in a cell, and is the same as a user (UE) in terms of functions. Direction communication between two devices is called device-to-device (D2D) communication.
A concept of the D2D communication is used in the fields such as a sensor network or WiFi Direct. Recently, cellular-based D2D communication has begun to be discussed even in a 3GPP system.
Meanwhile, if service continuity from a cellular communication session to a device-to-device communication session is provided when two terminals performing cellular communication approaches each other, resources of a network can be reused. However, a procedure of switching terminals performing cellular communication to device-to-device communication or switching terminals performing device-to-device communication to cellular communication is not defined.